1. Field of the Invention
The present invention relates to injection molding machines and, more particularly, to a die closing device which has a stationary die backplate or clamping plate and a movable die clamping plate driven by a toggle lever.
2. Discussion
Injection molding machines generally have a movable die clamping plate and at least one stationary die clamping plate. Depending on the driving means, such so-called two-platen machines can be used, although the driving means may itself be supported on a third auxiliary plate.
When two-platen machines without tie bars are employed, an important consideration is the parallelism of the mold, i.e. the correspondence or coordination of the die clamping plates. German patent publication DE 43 08 962 A1 discloses an injection molding machine wherein force transmission elements are constructed as separate deformation elements in the form of stirrups. The support plate is mounted at the machine base for movement in the closing direction.
Due to repeated deformations in normal use, the elements of these machines are subject to extensive wear and thus have a short service life. Furthermore, the deformation is force-dependent and the parallelism of the mold is, accordingly, not always provided.
European Publication 0 554 068 discloses an injection molding machine with a closing device wherein the stationary and movable die clamping plates are connected to each other through stirrups or clips and the force is imparted through the principal axis of the machine.
When a toggle lever drive is used for the closing device, a support plate is used as a third plate.